Voltage transformation apparatus



1942. R. H. SULLlVAN ETAL 3 VOLTAGE TRANSFORMATION APPARATUS Filed Nov. 24, 1933 Fya IN VENTDHS i% 1 Raymond hf Sullivan MAY/12am hf h'uzclu'ns Cyrz'l' Z1; Wa /111s WATTORNEYI Patented Dec. 22, 1942 VOLTAGE TRANSFORMATION APPARATUS Raymond H. Sullivan, William H. Hutchins, and Cyril T. Wallis, Rochester, N. Y., assignors, by mesne assignments, to General Motors Corporation, Detroit, Mich., a corporation of Dela- Application November 24, 1933, Serial No. 699,522

28 Claims.

This invention relates to voltage transformation apparatus, and more particularly to strucv ture and a circuit for interrupting the current flow from a source, as wellas for rectifying an alternating potential.

Altho quite a number of devices have been developed for accomplishing similar purposes, and particularly for the purpose of providing the high potentials necessary for the operation of an automobile radio receiver from the automobile storage battery, refinement and improvement are very desirable to increase the life, ruggedness, efficiency and operation of such devices so that they may better serve their purpose of eliminating more expensive and cumbersome apparatus.

It is therefore an object of this invention to provide rugged and eflicient interrupting and rectifying apparatus, which apparatus has long life and good operating characteristics.

Another object of this invention is to provide mechanical interrupting and rectifying apparatus that is compact and may be easily and cheaply manufactured.

Another object of this invention is to provide apparatus employing a vibrating reed for actuating contacts for rectifying an alternating potential, which apparatus embodies means for minimizing sparking at the contacts actuated by the reed, and means for reducing and tending to eliminate high or radio frequency currents in the circuit of which said contacts are a part.

Another object of this invention is to provide apparatus embodying a vibrating reed for actuating both interrupting and rectifying contacts, which apparatus embodies means for minimizing sparking at the contacts and has condensers intimately associated therewith to by-pass and tend to eliminate high or radio frequency currents in the circuit of which the secondary contacts are a part.

Another object of this invention is to provide apparatus embodying a vibrating reed and having an improved magnet motor for actuating the vibrating reed.

Another object of this invention is to provide apparatus embodying a vibrating reed having contacts mounted thereon and cooperating resiliently mounted contacts on either side of the vibrating reed, which apparatus embodies a substantially U-shaped frame member with the reed and resilient contact supports'insulatingly supported between the ends of the frame and an actuating magnet secured to'the frame at a point opposite the end of the reed so that the electromagnet core extends substantially parallel to the axis of the reed and in close proximity to an armature mounted on the end of the reed.

Another object of this invention is to provide apparatus embodying a vibrating reed and a magnet motor for actuating the, reed, in which the magnet has a core having an end projecting therefrom, and cooperating magnetic members providing a magnetic circuit from the end of the core opposite the projecting end to close proximity with the projecting end.

Another object of this invention is to provide apparatus embodying a vibrating reed having an armature on the end thereof and a magnet motor for actuating the reed; the magnet having a projecting notched core portion cooperating with magnetic members that form a partial magnetic path between an end of the core and the projecting portion thereof, said magnetic members and notched portion having surfaces substantially parallel to and spaced from said armature.

Further objects and advantages of the present invention will be apparent from the following description, reference being had to the accompanying drawing wherein a preferred embodiment of the present invention is clearly shown.

In the drawing:

Fig. 1 is a circuit diagram of a preferred em-' bodiment ofthe present invention.

Fig. 2 is a side elevation of a preferred structural embodiment of the present invention.

Fig. 3 is a fragmentary elevation taken substantially in the direction of the arrow 3 in Fig. 2.

Fig. 4 is a view of the actuating magnet structure taken substantially along the line, and in the direction of the arrows 4-! of Fig. 2.

Fig. 5 is a fragmentary sectional view of the actuating magnet structure, and is taken substantially on a line, and in the direction of the arrows 5-5 in Fig. 4.

Fig. 6 is a magnified or exaggerated view showing a preferred arrangement of the contacts, and taken substantially on a line and in the direction of arrow 66 of Fig. 2.

With particular reference to Fig. 1, a transformer in has a core It, a primary winding N that is preferably divided so as to have sections I6 and I8 and a center tap 20, and a secondary winding 22 having a center tap 24. The center tap 20 of the primary winding is preferably connected thru an inductance or choke 26 to one terminal of a battery 28. The ends of the primary winding I4 are connected to contacts 30 and 32 respectively, which contacts are engageable with contacts 34 and 36 respectively, that are mounted on a resilient reed or contact carrying member 38 and are electrically connected thereto. The resilient reed 38, in this form, is normally unbiased so that the contacts are normally in a. disengaged position. The vibrating reed 38 is preferably connected to ground at 40, and is connected to the other terminal of the battery 28 through a switch 42, and preferably thru an inductance or choke 44. An electromagnet 46 has a core 48 in magnetic relation with the reed 38 and a winding 58, one end of which winding is connected to a primary contact such as 32 while the other end is connected to ground at 52.

The ends of the secondary winding 22 are connected to contacts '54 and 56 respectively, which contacts are alternately engageable with contacts 58 and 68 respectively. The contacts 68 and 68 are mounted on the resilient reed 38, and electrically connected thereto. The secondary center tap 24 is connected to a suitable output lead 62 preferably thru an inductance or radio frequency choke 64 and an inductance or audio frequency choke 66, which choke coils are not particularly a part of the present invention, but rather, provide part of a filter to adapt the device to be utilized for supplying potential to a device such as a radio receiver. A condenser 68 is connected to the center tap 24 and to ground at 18. The vibrating reed 38 is connected to another suitable output lead 12 thru the inductance or choke 44. Condensers 14 and 16 are respectively connected to the ends of the audio frequency choke 66, and to the output lead 12, which condensers also form a part of the filter. Condensers 18 and 88 each have one side connected to the resilient reed 38, and the other side of the condenser 18 is connected to the contact 54 while the other side of the condenser 88 is connected to the contact 56.

With particular reference to Figs. 2, 3, 4 and 5, the structure of a preferred form of vibrator unit, to be used in a circuit such as that shown in Fig. 1, is illustrated. In these figures, reference numerals similar to those previously used refer to similar parts. In this structure, a preferably substantially U-shaped frame I08 having arms I82 and I84 and a closed end I86 is utilized as a support. This frame is preferably made of a metal or conducting material having comparatively low temperature coemcient of expansion. The contact and vibrator assembly comprises spacers I88, H8, H2, H4 and H6 that are preferably metallic; insulating spacers II8, I28, I22, I24, I26, I28 and I38; and metallic shims I32 and I34; as well as resilient contact springs I36, I38, I48 and I42; contact carrying spring reenforcing and stop members I44, I46, I48 and 158; and the resilient reed 38. The assembly formed by these parts is clamped and secured between the ends,of the arms I82 and I84 by screws I52 and I54 having cooperating nuts I56 and I58 and cooperating washers I68, I62, I64 and I66; or other suitable fasteners. The screws I52 and I54 are insulatingly separated from the contact carrying springs and the resilient reed by insulating spacers, not shown, or other suitable insulating means. The insulating spacers II8, I28, I22, I24, I26 and I28 insulatingly separate the current carrying parts of the assembly, such as the contact carrying springs and resilient reed, from each other, and also, in cooperation with the metallic spacers I88, H8, H2, H4 and H6, and the insulating spacer I30, as well as the stop members I44, I46, I48 and I58, properly space the contact carrying members from the resilient reed so that by minor adjustment of the contact carrying members and stop members, the stationary contacts are properly positioned for engagement with the reed contacts during vibration of the reed. The contact carrying springs, stop members and resilient reed preferably extend substantially parallel to each other and substantially parallel to the arms I82 and I84 toward the end I86 of the frame. The extending ends of the stop members I44, I46, I48 and I58 are preferably bent outwardly toward their respective contact carrying springs I36, I38, I48 and I42, and those contact carrying springs are preferably biased against the ends of those stop members so that the position of the contacts that are carried by the contact carrying members may be adjusted by bending the stop members, and vibratory movement of the contacts and their carrying members is limited.

The resilient reed 38 is preferably provided with a connecting lug such as I18, which lug is preferably grounded to the frame I88 thru a lead I12 that is preferably soldered to the frame as at I14 and I16. The contact carrying springs also preferably have connecting lugs such as a lug I18 on the spring I36 that is connected to a lead such as I88; 9. lug I82 on the spring I38 that is connected to leads such as I84 and I86; a lug I88 on the spring I48 that is connected to a lead such as I88; and a lug I92 on the spring I42 that is connected to a lead such as I84. A lead such as I86 is connected to the lug I18 for the purpose of making external connections to the resilient reed 38. The insulating spacer I38 preferably has an opening I88 therethru, thru which the leads I88, I84, I88, I94 and I86 extend. This provides an anchor and guide for the leads.

The resilient reed 38 preferably has secured to the surface thereof, such as at 288, a covering or layer of fibrous material such as cloth or paper to deaden the sound thereof and quiet the operation of the device. An armature 282 of magnetic material is secured to the end of the reed by rivets such as 284 or other suitable fastening means. This armature preferably has a portion 286 that extends beyond the end of the reed.

The core 48 of the electromagnet 46 preferably has a portion 288 that projects beyond the end of the winding 58 and extends thru an aperture 2I8 in a magnetic member 2I2 and an aperture 2 in the end I86 of the frame. The electro magnet is then secured to the end of the frame by riveting the end of the portion 288 as at 2I8. The other end of the electromagnet core preferably has a portion 2I8 that projects beyond the end of the winding and provides a shoulder as at 228 which provides a support for an insulating winding support member 222. The portion 2I8 preferably has an offset portion 224 such that the end of the core presents two substantially parallel end surfaces that are not in the same plane, and a surface 226 that is preferably sub stantially perpendicular to the parallel end sur faces. The magnetic member 2| 2 has side portions '228 and 238 that are preferably substantially parallel to the longitudinal axis of the core and which act as pole pieces that preferably have pole tips 232 and 234, which pole tips project toward the portion 2I8 of the core. Edges 236 and 238 of the pole tips 232 and 234 respectively are preferably substantially parallel, and preferably substantially in alignment with the surface 226 of the portion 2I8. End surfaces 240 and 242 of the pole tips 232 and 234 respectively, which surfaces form the pole ends or faces, are preferably curved so that their distance apart and their distance from the edges 244 and 246 of the portion 2I8 increases with the distance from the edges 236 and 238 respectively. This construction and arrangement results in an increase in the reluctance of the flux path between the magnetic pole surfaces with the distance from the edges 236 and238 or across the pole faces in one direction. The tendency of this construction and arrangement is therefore to increase the flux density toward one side of the pole tips. A disclike member of insulating material 248 located intermediate the end of the winding 58 and the magnetic member 2I2 provides an insulating support for the end of the winding. The winding is preferably insulatingly separated from the core by a layer of insulating material 258, and is preferably covered by a layer of insulating material 252.

The relative location of the armature 286 and the magnetic circuit provided by the pole tips 232 and 234 and the core portion 2I8 is preferably such that the armature is eccentric to the pole tips and to the magnetic flux threading the pole tip, altho in close proximity thereto.

In this preferred embodiment of the present invention, the condensers I8 and 88 are preferably secured to offset portions 256 and 258 of the arms I82 and I84 intermediate those arms and the resilient reed 38. These condensers preferably have metallic containers which serve as one terminal thereof so that the condensers are thus grounded to the frame and connected to the resilient reed through the lead H2. The condensers are preferably mounted so that the other connecting leads 268 and 262 thereto are connected to the contact carrying springs I36 and I38 in a manner such that the leads are short.

As indicated in the magnified or exaggerated view shown in Fig. 6, the primary contacts 38 and 32 are preferably adjusted so that the normal gaps intermediate the contacts 38 and 34 and the contacts 36 and 32 are less than the gaps between the contacts 54 and 58 and the contacts 68 and 56 respectively. This may be accomplished by either adjusting the contacts 38 and 32 so that they are closer together or by spacing the contacts 34 and 36 from the reed 38, or in some similar manner. This feature permits the primary circuit to be closed before and opened after the secondary circuit.

In the operation of this device in the circuit shown, the resilient reed' 38 is normally unbiased, so that the contacts 38 and 34, 36 and 32, 54 and 58, and 68 and 56 respectively, are normally disengaged. When the switch 42 is closed, the circuit is closed from one side of the battery 28 to the reed 38 and to ground at 48. This completes a circuit to the electromagnet winding 58 thru the primary winding section I8 since one end of the winding is grounded at 52 and the other end of the winding 58 is connected to the battery thru the primary winding section I8. The circuit thus formed thru the electromagnet winding effects a current flow therethru and causes the electromagnet to actuate the reed and move it to a position such that engagement of the contacts 36 and 32 and 68 and 56 respectively is effected. The engagement of the contacts 36 and 32 short circuits the electromagnet winding 58 by connecting the end thereof to ground at 48 thru those contacts. The resulting deenergization of the electromagnet releases the reed so that its resilience, deformation and mass carry it to a position to effect engagement of the contacts 54 and 58 and 38 and 34 respectively. Similar cycles of operation result in vibration of the reed at a rate dependent upon the natural vibrating period and thus alternate making and breaking of the contacts.

When the contacts 36 and 32 are closed, the current flow thru the section ll of the primary winding creates a flux that produces a potential in the secondary winding 22. This secondary potential is applied to the output lead 62 from the center tap 24, and to the output lead 12 thru the contacts 68 and 56. Engagement of the contacts 38 and 34 closes a circuit thru the section I6 of the primary winding after the disengagement of the contacts 36 and 32 opens the circuit thru the section I8. The resulting flow of current thru the section I6 of the primary winding creates a flux in a direction opposite to that which was created by the section I8. This, in turn, in-' duces a potential in the secondary winding 22 opposite in polarity to that produced by the current in the section I8. However, the potential applied to the output leads 62 and I2 is of the same polarity in each instance, since the other end of the secondary winding is connected to the output lead I2 thru the contacts 54 and 58. The resistance of the electromagnet winding 58 is preferably high so that the current flow thru the section I8 of the primary winding and the electromagnet, while the contacts are open, as well as its shunt effect across the section I6 are not appreciably high with respect to the current flow thru the sections I8 and I6 when the contacts 36 and 32 or 38 and 34 respectively, are closed.

It has been found that unless some means are provided for the prevention of sparking'at the contacts, and the improvement of the efiicieny of the device, that the sparking is detrimental to the life and operation of the unit and the emciency is considerably reduced. Hence, the condensers I8 and 88 have been provided, each of which condensers is connected from the reed 38 to a secondary contact or end of the secondary winding. Furthermore, these condensers, connected in this manner, provide a by-pass or conductor path for reducing and tending to eliminate high and radio frequency currents from the secondary circuit, as well as from the primary circuit when the primary circuits are closed. These high and radio frequency currents are bypassed to ground at 48. Hence, the leads 268 and 262 are preferably made as short as possible to increase the effectiveness of this by-passin action and to prevent radiation therefrom. By utilizing the metallic or conductive container for the condensers I8 and 88, and utilizing that container as a terminal for one side of the condenser, the condensers are easily and conveniently grounded directly to the frame I88 by sol dering or similar means.

It has also been found that by mounting the contacts 38, 32, 54 and 56 on resilient contact carrying members, and adjusting the position of the contacts 38 and 32 so that contact is made between the contacts 36 and 32 somewhat before contact is made between the contacts 68 and 56, the characteristics and efiiciency of the circuit are further improved.

To make the operation of the condensers I8 and 88 more clear to those skilled in the art, and to explain more fully how the reduced contact sparking and increased efficiency are obtained through the use of these condensers, the following discussion, together with approximate mathematical representations are herein presented. Broadly, when the reed swings from one side to the other, the circuit to the primary winding opened on one side and closed to the other side. This causes the magnetic flux to reverse in rection. Therefore, the flux builds up to a max imum value in one direction, then drops to zero and builds up to a. maximum value in the other direction. This alternating magnetic field gencrates an alternating voltage in both the primary and the secondary windings. The second set of contacts on the reed vibrates in synchronism with the primary circuit interrupting contacts to rectify the alternating voltage and currents of the secondary windings.

At the time when the primary current and the magnetic field are building up, the counter E. M. F. or voltage generated in the primary winding at any instance after closing the primary circuit, may be represented by:

Where: ep =the voltage induced in the primary w nding. Np the number of turns in the primar winding.

%%:the rate of change of the magnetic field. (I,

The sign in front of the right member of the Equation 1 shows that the induced voltage opposes the impressed battery voltage Neglecting the resistance of the primary winding, at any instant:

Eb -Gp where Ee the impressed battery voltage.

The voltage generated in the secondary coil by the changing magnetic field is:

, a dt volts From (1) and (4) it may be seen that the ratio ever, the polarity of the induced voltage in this instance is reversed to that of the first instance.

When the primary contacts are closed:

E e or where:

c c the voltage generated in the primary winding at any time (t) after the primary contacts are closed.

L :the inductance of the primary circuit in henries.

R :the primary resistance in ohms.

c :a constant (2.718)

t :the time in seconds that the primary contacts are closed.

In systems such as the present, where the primary and secondary windings are interlinked with the completely closed magnetic circuit, the resistance of the primary winding is comparafill 'ered as zero for practical calculations.

tively low, and the time t is comparatively small, the value of the exponent in ('7) is practically zero, and may be consid- Therefore, Equation 7 becomes:

must be constant. That is:

and, solving (11) for When the primary contacts are opened, and if no resistance or capacity is shunted across the primary contacts or secondary contacts or the primary or secondary windings or both, the inductive voltage across the contacts will tend to increase to an indefinitely large value. However, in such an instance, an are forms at the con tacts and has the same ffect as connecting a resistance across the contacts or primary or secondary windings. Such an arc, as well as being harmful to the contacts, dissipates energy and is in effect a power loss. This condition may be shown mathematically as follows:

po=the primary voltage at any time (t) after the primary contacts are opened. From (13) it may be seen that if the resistance across the contacts is indefinitely large at the time of opening the contacts, the exponent m: w volts If a very low value of resistance were connected across the contacts or windings, the ex- Equations 14 and 15 show that it is necessary to have some resistance or some equivalent suppressor across the contacts or one or both of the windings if the voltage across the contacts is to be kept below any value that will create an are at the contacts. These equations also indicate that for best results, the effective value of this suppressor or resistance should be kept within predetermined limits. The desired result, in this respect, is therefore to control the voltage across the contacts with rwpect to the separation of the contacts so that sparking is reduced or eliminated. By connecting the condenser or condensers of the proper capacity across the contacts or primary or secondary windings, this result may be quite einciently attained.

When the primary contacts are closed, the current flow through the primary winding builds up a magnetic field in the magnetic circuit or core. Energy from the battery is required to establish or build up this magnetic field. Therefore, the magnetic field interlinking the primary winding at the time of opening the primary contacts represents stored magnetic energy.

When, therefore, condensers are utilized for the reduction or elimination of sparking at the con tacts, the voltage generated in the transformer windings by the decay of the magnetic ilux in the core, charges the condenser. The storedmagnetic energy is thus transformed into electrostaticenergy.

The magnetic energy stored in the magnetic circuit at the time when the primary contacts are open may be represented by the following equation:

where:

'W=the electrostatic energy in joules;

C=the capacity of the condenser in farads; and e=the peak voltage across the condenser.

Since the same energy is merely transformed in form from magnetic to electrostatic energy, and neglecting the resistance energy loss, which is negligible in a circuit having low resistance such as that in the present system, the electroenergy, thus Wm=We (I8) and L. .e.= eg1. (19) The frequency of energy transformation from one form to the other is dependent upon the natural electrical period of the circuit. That is,

1 j=m0 P. S. (20) The peak value of the voltage across the condenser and winding occurs twice in a cycle; that is, there is a positive and a negative peak. The first peak value of voltage occurs at the time of the first quarter cycle after the contacts are opened.

j where f=the frequency in cycles per second; and T=the time for one discharge cycle.

T= 1 =2 /ITC seconds 22 The time in seconds required for the first quarter cycle is denser that is connected across the contacts, or.

across a winding. Since the contacts are in engagement before they are opened or separated, the voltage across the contacts is zero at the instant of separation and increases to a maxi- That is, after the time of contact separation, there is a steady increase in the voltage across the contacts. Also, after the instant of separation, there is a steady increase in separation between the contacts. It, then, arcing of the contacts is to be eliminated, the ratio of the rate of voltage rise across the contacts to the rate of contact separation must remain below that at which arcing will occur. It is easily understood "that substantially the same result, in this respect, can be obtained by connecting a condenser across the primary or secondary winding, or across the respective contacts.

- Eince the effect of a condenser connected across an inductance or winding, as in the present instance, is to shift the phase of the current in the winding with respect to the voltage, and consequently to shift the phase of the induced voltages, it may be seen that such a condenser or condensers, when of. the proper value, may be easily and conveniently utilized to bring the points of zero current value of the secondary current into synchronism with the P ints of interruption of the primary current; or to adjust the time constant of the secondary circuit to synchronism to that of the primary synchro nism. This is desirable in the present instance, since both the primary and secondary contacts static energy stored is equal to the magneticjw' are actuated by a single reed. Furthermore,

since the beneficial result of the condenser for storing magnetic energy does not increase with the size of that condenser after a predetermined capacity is reached, a value of condenser capacity is chosen which most nearly effects the desired ultimate result of eliminating sparking at the contacts and improving the emciency of the system.

By connecting two condensers in series across the secondary winding, and grounding the COllimon connection of those condensers, as shown in the present form of this invention, the can densers serve to accomplish still another purpose; namely, that of providing a by-pass to [6 ground for high and radio frequency currents.

the claims which follow.

What is claimed is as follows:

1. In combination with a transformer having primary and secondary windings, a vibrating means having a single magnetic vibrator motor, and provided with series of contacts for interrupting a primary current and for rectifying an alternating secondary voltage, some of said contacts also controlling the magnetic vibrator motor, and means for reducing sparking at the contacts, the last mentioned means also providing a by-pass tending to eliminate high and radio frequency currents from the rectifying contacts.

2, In combination with a transformer having primary and secondary windings, a vibrating means having a single magnetic vibrator motor, and provided with series of contacts for interrupting primary current and for rectifying an alternating secondary voltage, some of said contacts also controlling the magnetic vibrator motor, and means for reducing sparking at the contacts, the last mentioned means also provida tiff-pass tending to eliminate high and radio frequency currents from the rectifying contacts, said last mentioned means comprising condensers having capacity suited to the reduction of sparking and each being connected to the vibrating means and to the rectifying contacts.

3. In combination with a voltage change device, a vibrating means having a single magnetic vibrator motor, and provided with series of contacts for interrupting a primary current and for rectifying an alternating secondary voltage, the contacts for interrupting the primary current also controlling the magnetic vibrator motor, means for bringing the points of zero current value of the secondary current substantially into phase with the interruptions of said primary current, said last mentioned means also providing a by-pass for high and radio frequency currents from the rectifying contacts.

4. In combination, a transformer having primary and secondary windings and vibrating means for interrupting a primary current and for rectifying a secondary voltage, said vibrating means being unitary and having a ground connection, means for changing the phase of the secondary current, the last mentioned means providing a by-pass for high and radio frequency currenw.

5. In combination, a transformer having primary and. secondary windings and circuits therefor, and vibrating means for interrupting a primary current and for rectifying a secondary voltage, said vibrating means being unitary and having a direct ground connection, and means for lay-passing high and radio frequency currents from one of said circuits to ground.

In combination, a transformer having primary and secondary windings and circuits therefor, and vibrating means for interrupting a primary current and for rectifying a secondary voltage, said vibrating means being unitary and having a direct ground connection, and means for by-passing high and radio frequency currents from one of said circuits to ground, the last mentioned means comprising a plurality of condensers connected to the vibrating means and to one of said circuits.

7. In combination, a transformer having primary and secondary windings and circuits therefor, and vibrating means for interrupting a primary current and for rectifying a secondary voltage, said vibrating means being unitary and having a direct ground connection, and condensers connected to the vibrating means and to the circuit of the secondary winding for bypassing high frequency currents from said circuit to ground.

8. In combination with avoltage change device having primary and secondary windings and circuits therefor, a vibrating means having a ground connection and a magnetic vibrator motor, and provided with series of contacts for interrupting a primary current and for rectifying an alternating secondary voltage, the contacts for interrupting the primary current also controlling the magnetic vibrator motor, and means for storing some of the magnetic energy of the voltage change device, that is present when the primary current interrupting contacts are opened, in-the form of electrostatic energy, the energy storing means also providing a by-pass to ground for high frequency currents.

9. In combination with a transformer having a tapped primary winding and a secondary winding and circuits therefor, a vibrator device having motive means connected to a source of primary current, and a set of contacts for controlling the motive means and for alternately connecting diiferent parts of the primary winding to the source of primary current to cause the flux in said transformer to vary from a positive to a negative value periodically, a second set of contacts connected with the secondary winding of the transformer to rectify the secondary voltage,

- and means for storing some of the magnetic that the voltage across the secondary contacts after those contacts are opened is reduced tolimit arcing at the contacts.

10. In combination with a transformer having a tapped primary winding and a secondary winding and circuits therefor, a vibrator device having motive means connected to a source of pri mary current, said vibrator device being grounded, and a set of contacts for controlling the motive. means and for alternately connecting different parts of the primary winding to the source of primary current to cause the flux in said transformer to vary from a positive to a negative value periodically, a second set of contacts connected with the secondary winding of the transformer to rectify the secondary voltage, and means for storing some of the magnetic energy that is present in the transformer at the time of breaking the contacts that control the primary winding, said means comprising condensers connected to the vibrator and to the contacts that are connected to the secondary winding, said condensers having a capacity such that the voltage across the secondary contacts after those contacts are opened is reduced to limit arcing at the contacts, and said condensers providing .a by-pass to ground for high frequency currents from one of the circuits.

11. In combination, a transformer having primary and secondary windings and a vibrating means for interrupting a primary current and contacts for rectifying a secondary voltage, and means for controlling the rate of secondary voltage rise in proper relation to the separation of said contacts to prevent arcing at the contacts, the last mentioned means comprising condensers each connected to said vibrating means and each connected to a secondary contact, said condensers also providing a by-pass for high frequency currents.

12. In combination with a transformer havin a tapped primary winding and a secondary winding and circuits therefor, a vibrator device having motive means connected to a source of primary current, and a set of contacts for alternately connecting different parts of the primary winding to the source of primary current to cause the flux in said transformer to vary from a positive to a negative value periodically, a second set of contacts connected with the secondary winding of the transformer to rectify the secondary voltage, and means for improving the efficiency of the combination, said means comprising condensers connected to said vibrator device and to one each of one of said sets of contacts and preadjusted contact carrying members so constructed and arranged that the primary contacts break after the contacts that rectify the secondary voltage. v

13. In combination witha transformer having a tapped primary winding and a secondary winding and circuits therefor, a vibrator device having motive means connected to a source of primary current, said vibrator device being grounded, and a set of contacts for alternately connecting different parts of the primary winding to the source of primary current to cause the flux in said transformer to vary from a positive to a negative value periodically, a second set of contacts connected with the secondary winding of the transformer to rectify the secondary voltage, and means for improving the efficiency and operation of the combination, said means comprising condensers, each of which. condensers is connected to said vibrator device and to a contact of one of said sets of contacts, said condensers serving both to limit sparking at the contacts and to by-pass high frequency currents, and means so constructed and arranged that the contacts of said sets make and break at different times.

14. In combination with a transformer having a primary winding and a tapped secondary winding and circuits therefor, a vibrator device having motive means connected to a source of primary current, and a set of primary contacts for controlling the motive means and for effecting intermittent energization of the primary winding from the source of primary current, a second set of contacts connected with the secondary winding of the transformer to rectify the secondary voltage, and means for improving the efficiency of the combination, said means comprising condensers connected to the vibrator device and to one each of one of said sets of contacts and preadjusted contact carrying members so constructed and arranged that contacts of one of said sets break after the contacts of the other of said sets.

15. In combination with a transformer having primary and secondary windings, a motor operated vibrating means provided. with series of contacts for interrupting a primary current and for rectifying an alternating secondary voltage and a capacity across the secondary Winding of the transformer for reducing high and radio frequency currents at the rectifying contacts, said capacity comprising a plurality of condensers connected to ground.

16. In combination with a transformer having primary and secondary windings, a motor operated vibrating means provided with, series of contacts for interrupting a primary current and for rectifying an alternating secondary voltage and a capacity across the secondary winding of the transformer for reducing high and radio frequency currents at the rectifying contacts, said capacity comprising a plurality of condensers and a connection extending from a point between the contacts to ground.

17. In combination with a transformer having primary and secondary windings, a motor oper-' ated vibrating means provided with series of contacts for interrupting a primary. current and for rectifying an alternating secondary voltage and a capacity across the secondary windingof the transformer for reducing high and radio frequency currents at the rectifying contacts, said capacity comprising a plurality of condensers connected in series and a connection from said condensers to ground.

18. In combination with a transformer having primary and secondary windings, a motor operated vibrating means provided with series of contacts for interrupting a primary current and for rectifying an alternating secondary voltage and means forming a by-pass operative to reduce high and radio frequency currents at the rectifying contacts and also operative to reduce sparking at the contacts, said means comprising a plurality of condensers across the secondary winding of the transformer and connectedto ground.

19. In combination with a transformer having primary and secondary windings, a motor operated vibrating means provided with series of contacts for interrupting a primary current and for rectifying an alternating secondary voltage and means forming a by-pass operative to reduce high and radio frequency currents at the rectifying contacts and also operative to reduce sparking at the contacts, said means comprising a plurality of condensers connected in series across the transformer and having a connection from a point between the condensers to ground.

20. In combination with a transformer having primary and secondary windings, a motor operated vibrating means provided with series of contacts for interrupting a primary current and for rectifying an alternating secondary voltage and means forming a by-pass operative to reduce high and radio frequency currents at the rectifying contacts and also operative to reduce sparking at the contacts, said means comprising a plurality of condensers connected in series across the transformer and having a connection from a point be. tween the condensers to ground at apoint between said condensers.

21. In combination with a transformer having primary and secondary windings, a motor operated vibrating means provided with series of contacts for interrupting a primary current, rectifying a secondary current and for controlling the operation of the motor for operating the vibrating means, and means forming a by-pass operative to reduce high and radio frequency currents at the rectifying contacts, said means comprising a plurality of condensers connected across the secondary winding of the transformer andto ground.

22. In combination with a transformer having primary and secondary windings, a motor operated vibrating means provided with series of contacts for interrupting a primary current, rectifying a secondary current and for controlling the operation of the motor for operating the vibrating means, and means forming a, by-pass operative to reduce high and radio frequency currents as the rectifying contacts, said means comprising a plurality of condensers connected in series across the transformer and to ground at a point between said condensers.

23. In combination with a transformer having primary and secondary windings, a motor operated vibrating means provided with series of contacts for interrupting a primary current, rectifying a secondary current and for controlling the cperation of the motor for operating the vibrating means, and means forming. a Fay-pass operative to reduce high and radio frequency currents at the rectifying contacts, said means being also operative to reduce sparking at the contacts and comprising a plurality of condensers connected across the secondary winding of the transformer and to ground.

24. In combination with a transformer having primary and secondary windings, a motor operated vibrating means provided with series of contacts for interrupting a primary current, rectifying a secondary current and for controlling the operation of the motor for operating the vibrating means, and means forming a by-pass operative to reduce high and radio frequency currents at the -rectifying contacts, said means being also operative to reduce sparking at the contacts and comprising a plurality of condensers connected in series across the secondary winding of the transformer and to ground at a point between said condensers.

25. In combination with a transformer having primary and secondary windings, a motor operated vibrating means provided with series of contacts for interrupting a primary current and for rectifying an alternating secondary voltage and means for bringing the points of zero potential value of the secondary voltage into synchronism with the interruptions of the primary current and for reducing high and radio frequency currents at the rectifying contacts, said means comprising a plurality of condensers connected across the secondary of the transformer and to ground.

26. In combination with a transformer having primary and secondary windingsya motor operated vibrating means provlded,with series of contacts for interruptinga primary current and for rectifying an alternating secondary voltage and means for bringing the points of zero potential value of the secondary voltage into synchronism with the interruptions of the primary current and for reducing high and radio frequency currents at the rectifying contacts, said means comprising a plurality of condensers connected in series across the secondary of the transformer and connected to ground at a point between said condensers.

27. In combination with a transformer having primary and secondary windings, a motor operated vibrating means provided with series of contacts for interrupting a primary current, rectifying a secondary current and for controlling the operation of the motor for operating the vibrating means, and means for bringing the pointsof zero potential value of the secondary voltage into synchronism with the interruptions of the primary current and for reducing high and radio frequency currents at the rectifying contacts, said means comprising a plurality of condensers connected across the secondary of the transformer and to ground.

28. In combination with a transformer having primary and secondary windings, a motor operated vibrating means provided with series of contacts for interrupting a primary current, rectifying a secondary current and for controlling the operation of the motor for operating the vibrating means, and means for bringing the points of zero potential value of the secondary voltage into synchronism with the interruptions of the primary current and for reducing high and radio frequency currents at the rectifying contacts, said means comprising a plurality of condensers connected in series across the secondary of the transformer aud'connected to ground at a point between said condensers.

' RAYMOND H. SULLIVAN. WILLIAM H. HU'ICHINS. CYRIL T. WALLIS. 

